1. Field of the Invention
The present invention relates to a power-on detecting circuit and a level converting circuit. More particularly, the present invention relates to a power-on detecting circuit and a level converting circuit that can stably detect a rise of a plurality of differing supply potentials without depending on an application sequence or a rise time of the supply potentials.
2. Description of the Related Art
Some semiconductor circuits, such as level converting circuits, operate at a plurality of supply potentials. A through current flows in such semiconductor circuits when an input potential does not rise sufficiently at a rise of a supply potential, particularly, when the input potential is a medium potential relative to the supply potential. Flow of a through current in a semiconductor circuit can lead to increase in power consumption, lowering of an output potential of a power supply circuit, or hinder a normal start of a system.
JP-A 2005-286675 (KOKAI) discloses a method of activating a plurality of input/output circuits with supply voltages larger than a first supply voltage, which activates an internal circuit, to enable stable operation of a circuit compatible with a plurality of supply voltages, without depending on an application sequence of the supply voltages. Specifically, a level shift circuit is provided that converts signal amplitude corresponding to the first supply voltage to signal amplitude corresponding to each of the supply voltages, and a first control signal is formed by a plurality of power detecting circuits until the first supply voltage and the supply voltages reach respective predetermined levels to control an operation of the input/output circuit to a predetermined operation corresponding thereto.
However, in the method disclosed in JP-A 2005-286675 (KOKAI), the supply voltage of the input/output circuit is used to detect the supply voltage of the internal circuit. This method works well when the supply voltage of the internal circuit has risen after the supply voltage of the input/output circuit has risen. However, this method does not work well when the supply voltage of the internal circuit rises before the supply voltage of the input/output circuit has risen.